Method and reactor for production of aluminum by carbothermic reduction of alumina

Abstract

A hollow partition wall is employed to feed carbon material to an underflow of a carbothermic reduction furnace used to make aluminum. The partition wall divides a low temperature reaction zone where aluminum oxide is reacted with carbon to form aluminum carbide and a high temperature reaction zone where the aluminum carbide and remaining aluminum oxide are reacted to form aluminum and carbon monoxide.

What is claimed is:  
     
       1. A process for carbothermic production of aluminum where a molten bath comprising aluminum carbide is produced in a low temperature compartment, which molten bath flows into a high temperature compartment where the aluminum carbide is reacted with alumina to produce aluminum which forms a layer above a molten slag; wherein the low temperature compartment and the high temperature compartment are located in a common reaction vessel and the low temperature compartment is separated from the high temperature compartment by a hollow underflow partition wall having an opening in the wall; the molten bath produced in the low temperature compartment continuously flows under the partition wall and into the high temperature compartment, and where additional carbon material is supplied to the flow under the partition wall through the opening in the hollow partition wall. 
     
     
       2. The process according to  claim 1 , wherein the hollow partition wall is vertically movable. 
     
     
       3. The process according to  claim 1 , wherein the amount of additional carbon material added to the slag is varied by controlling the speed of movement of a transport means supplying carbon material to the flow under the partition wall. 
     
     
       4. The process according to  claim 1 , wherein the off-gases from the low temperature compartment and from the high temperature compartment are reacted to form Al 4 C 3  and the Al 4 C 3  is fed to the flow under the wall. 
     
     
       5. The process according to  claim 3 , wherein the carbon content of the slag in the high temperature compartment is measured and fed back to the transport means. 
     
     
       6. The process according to  claim 1 , further comprising sensing the amount of carbon in the slag of the high temperature compartment and varying the amount of carbon material added through the particles wall accordingly. 
     
     
       7. The process according to  claim 1 , wherein the tapped aluminum contains aluminum carbide, and wherein the aluminum carbide is precipitated and the purified aluminum is alloyed and then cast into alloyed aluminum shapes, said aluminum carbide being fed as additional carbon material to the flow under the wall. 
     
     
       8. The process according  claim 1 , wherein the tapped aluminum contains aluminum carbide, and wherein said tapped aluminum is cooled to precipitate the aluminum carbide, followed by filtering, degassing, and then casting in an ingot casting machine to form aluminum shapes, said precipitated aluminum carbide being fed as additional carbon material to the flow under the wall. 
     
     
       9. A reactor for carbothermic production of aluminum, comprising a reaction vessel comprising a low temperature reaction compartment having means for supply of materials to said compartment and one or more electrodes for supplying electric operating current to said compartment, said electrode or electrodes being positioned for submersion in a molten bath in the low temperature compartment; 
       a high temperature compartment separated from the low temperature compartment by means of a hollow partition wall allowing underflow of molten bath from the low temperature reaction compartment into the high temperature compartment, said wall having an opening and a transport means feeding additional carbon material to the underflow through the opening in the hollow partition wall;  
       electrodes arranged in a sidewall of the high temperature compartment of the reaction vessel for supply of electric current to said compartment;  
       means for injecting material into the high temperature compartment; and  
       an outlet for continuously tapping molten aluminum from the high temperature compartment.  
     
     
       10. The reactor according to  claim 9 , wherein the reaction vessel has a substantially rectangular shape, and wherein the partition wall is vertically movable. 
     
     
       11. The reactor according to  claim 9 , wherein the transport means is variable to control the rate of feed of the additional carbon material to the underflow. 
     
     
       12. The reactor according to  claim 9 , further comprising a sensor to detect the carbon content in the high temperature compartment. 
     
     
       13. The reactor according to  claim 9 , wherein the one or more off-gas reactors are connected to the reactor compartments for producing Al 4 C 3  and a hopper is used to supply carbon material to the hollow partition wall. 
     
     
       14. The reactor according to  claim 13 , further comprising means for supplying to the hopper the Al 4 C 3  produced in said off-gas reactors. 
     
     
       15. The reactor according to  claim 9 , wherein the transport means comprises at least one screw. 
     
     
       16. The reactor according to  claim 9 , wherein the hollow partition wall defines a plurality of spaces each with a separate transport means. 
     
     
       17. In a reactor for producing aluminum by carbothermic reduction of alumina having a single reactor with two compartments, a high temperature reaction compartment and a low temperature reaction compartment, and an underflow partition wall that separates the two compartments where slag flows under the partition wall from the low temperature compartment to the high temperature compartment, the improvement comprising: 
       a supply means for supplying additional carbon material through the underflow partition wall to the slag flowing from the low temperature compartment to the high temperature compartment.  
     
     
       18. The reactor of  claim 17 , wherein said supply means includes a hollow area in said partition wall and one or more openings in said wall, said one or more openings being in the lower portion of said wall to connect said hollow area with said flow. 
     
     
       19. The reactor of  claim 17 , wherein said supply means includes one or more conduits positioned in said partition wall, each conduit having an opening in the lower portion of said partition wall which connects said conduit with said flow. 
     
     
       20. The reactor of  claim 17 , wherein a hopper is in communication with said supply means to provide said supply means with said additional carbon material.